Electroconductive paper

ABSTRACT

An electroconductive paper useful in electrostatic image reproduction techniques containing a polymer comprising units of the formula:   WHEREIN R is H or CH3, R1 is hydroxyethyl or hydroxypropyl group, R2 is a (C1-C4) alkyl group R3 is a (C1-C4) alkyl group, and X is an anion.

United States Patent Inventors Raymond W. McNamee, Jr.

Horsham; Norman Shachat, Levittown; Frank J. Glavis, Rydal, all of Pa.

Appl No. 851,744

Filed Aug. 20, 1969 Patented Nov. 2, 1971 Assignee Rohm and Haas Company Philadelphia, Pa.

ELECTROCONDUCTIVE PAPER 8 Claims, No Drawings U.S.Cl 1l7/201, 117/34,96/1.5,96/1.8

Int. Cl 603g 7/00, B44d l/00 Field of Search 1 17/201,

[56] References Cited UNITED STATES PATENTS 3,335,100 8/1967 Geyer 117/201 X 3,348,970 10/1967 Gess 117/201 Primary Examiner-William L. Jarvis Attorneys-Carl A. Castellan and George W. F. Simons ABSTRACT: An electroconductive paper useful in electrostatic image reproduction techniques containing a polymer comprising units of the formula:

wherein R is H or CH R is hydroxyethyl or hydroxypropyl group, R is a (C,-C,) alkyl group R is a (C,C,) alkyl group, and X is an anion.

ELECTROCONDUCTIVE'PAPER DESCRIPTION OF THE INVENTION Electroconductivepaper may be used to distribute electrical stresses in various insulating productsysee, for instance,

U.S. Pat. No. 3,148,107. Where electrically conductive paper :is tobe usedfor nonimpact printing, a substrate, backing,'im-

other processes. As a rule, such processes call for'the placing of an electriecharge on the paper. This may be accomplished by a corona discharge, for example, and in most processes, the electrical charge is placed on the paper in darkness.

The paper may also be provided with or contain .a ;photoresponsive or photoconductivematerial or layer. At present,

there is popularly used a specially treated zinc oxide coating on the paper. Where light strikes portionsof the paper treated with such a light-sensitive material, the electrical charge is-dis' sipated in those areas exposed to the light. As a result,.there is left a pattern of charged and uncharged areas.

The charged area will then be efiective .to attract 'an-oppositely charged powdered, or other usually particulated, image-forming material. Such a powder will not be attracted to the light-affected discharged areas, and the powdermay thus be deposited onrthe paper in a pattern tocorrespond with charged areas. Generally, such an image-forming material may then be fused, or otherwise treated, on the paper to make the image permanent. Such a material, presently used, isa wax-coated finely divided carbon-black, which will fuse when heated on the paper.

Other processes for electrostatic reproduction differ from the above in thatthe image is created by electricaldissipation of the static charge in nonimage areas. -ln this and certain other processes (see the Vaurio and Fird reference mentioned above), the common characteristic is again an electrically conductive base paper. This electrically conductive layer of the paper assures a rapid discharge of the charge when and where desired, and also aids in an even distribution of the initial charge.

Probably the most common copy reproduction system of the above types used at present is the direct electrostatic process; see, e.g., Chemical and Engineering News, July 20, 1964, pp. 88-89 and U.S. Pat. No. 3,052,539. This process is similar to the xerographic method of copy reproduction; however, the conductive substrate is built into the paper rather than being on .a separate drum or other device. Otherpatents relating to conductive paper for electrostatic reproduction inelude U.S. Pat. Nos. 3,264,137 and 3,248,279.

Some quaternary ammonium group-containing polymers have been used in the making of electroconductive paper. Thus U.S. Pat. No. 3,01 1,918 mentions the use of vinyl benzyl quaternary ammonium compounds. However, these polymers have extremely unpleasant odors. Consequently, the unpleasant fishy odor associated with them makes the operation of coating the paper an unpleasant one and also tends to leave the paper product with a strong residual fishy odor. In U.S. Pat. No. 3,264,137 there are disclosed besides the vinyl benzyl quaternary ammonium compounds some acryloxyalkyl quaternary ammonium compounds in which the quaternary nitrogen carries either three alkyl groups or two alkyl groups and a benzyl group. The former are beset with the same unpleasant fishy odor as the products of U.S. Pat. No. 3,01 1,918 but the latter have an undesirable tendency to loseconductivity on storage.

The present invention provides improvements in paper having electroconductive coatings for use in the aforesaid insulating products and in electrostatic-copy-reproduction methods.

It has now been discovered that certain polymers having pendant quaternary ammonium groups attached to an essentially linear polymer, having a carbon-to-carbon atom =backbone .chain, through an ester linkage, and containing "hydroxyethyl or "hydroxypropyl groups attached to the nitrogen atom, are ofspecial value to provide a papersub- "strate 'with an electroconductive coating. The ester-type :polymers prepared with hydroxyethyl and/or hydroxypropyl :groups attachedto the nitrogen atom do not -have an unpleasantfishy odor and they have farless tendencyto lose conductivity with time than do comparable acrylic ester polymersprepared heretofore which have threealkyl groups (or twoalkyl groups and one benzyl group) attachedto the quaternarynitrogen atom. Accordingto this invention the polymers which may beused willige'nerally'haveamolecular weight sufficient to formaclearself-supporting'filmof-about one-half-to 2-microns'thickness, when dried from an aqueous solution, with repeating units of the formula:

medium using a catalyst, as in the polymerization of dimethylaminoethyl methacrylate by well--known techniques. The water-soluble linear polymers of the present invention may have molecular weights in the range of about 10,000 to 2,000,000 or more and may be made by the direct polymerization ofaminoalkyl esters ofacrylic or methacrylic acid ortheir salts to form a homopolymer of any one of them or a copolymer of any two or'more thereof, and then quaternizing at least 75 percent of the amine-containing units with an alkylene oxide. The quaternized polymers may have molecular weights of about 20,000 to 2,000,000. Specific examples are the :polymers-of dimethylaminoethyl acrylate and methacrylate, diethylaminoethylacrylate and methacrylate, 3-dime'thylor 3-diethylarninopropyl acrylate and methacrylate and 2- dimethylaminoisopropyl acrylate and methacrylate and their salts which are quaternized with-ethylene oxide or propylene oxide. In all these cases, the proportions of monomers are so selected as to provide a polymer containing at least 75 mole percent of the alkyleneoxide-quaternized aminoalkyl ester of acrylic acid or methacrylic acid and preferably mole percent to mole percentthereofin the copolymer molecule.

Alternatively the conductivity aids of the present invention may be prepared by first forming a monomer containing quaternary ammonium groups and having the formula:

i HgC=C-COOAN X- (II) I t R by reacting an amino-containing monomer of the formula I H2c=c-c o OAN (III) with ethylene oxide or propylene oxide to quaternize 75 to 100 percent of it. Then the resulting monomer or monomer mixture may be polymerized to form a homopolymer or a copolymer containing up to 25 mole percent of the dialkylaminoalkyl ester units.

When polymers in the lower molecular weight range are desired, the polymerization of the amine, its salt, or its quaternary may be effected at elevated temperatures, e.g. 40 to 60 C. or higher using conventional initiator systems, such as ammonium persulfate with or without sodium hydrosultite. The higher molecular weight polymers may be obtained at lower temperatures, such as 5 to C. and using concentrations of 60 percent or more with dilution to facilitate handling as polymerization progresses.

The amine-containing monomer or polymer may be alkylated with ethylene oxide or propylene oxide or a mixture thereof by introducing with the necessary autogeneous pressure an equivalent quantity (or excess thereof) of the oxide into a closed vessel containing a solution of the monomer or polymer at a temperature of 35 to 50 C. over a period of several hours.

Preparation of the polymers used in the present invention is illustrated by the following procedure:

EXAMPLE A The hydrochloride of dimethylaminoethyl methacrylate (268 grams) is dissolved in water (618 grams). The solution is purged over one hour at 45 C. Then ammonium persulfate (4.24 grams) is added, and 2 minutes later a solution of 2.04 grams of hydrosulfite is added. The polymerization exotherms from 45 to 65 C. in 30 minutes, and thickens. The solution is held at 65 C. for one hour. The polymer solution is cooled to 30 C. and then introduced into an autoclave and 70 grams of ethylene oxide is added at 30 C. After two hours at autogeneous pressure the resulting product has 30 percent total solids, a pH of about 6.5 and a Gardner-Holdt viscosity of 10,000 cps. The polymer contains about 75 mole percent of methacryloxyethyldimethyl (2-hydroxyethyl) ammonium chloride units and has an estimated molecular weight of about 25,000 viscosity average.

To prepare an electroconductive paper, the N-hydroxy alkyl quaternary ammonium polymers hereinabove defined may be applied to the paper, or cellulosic web, by the conventional methods used for that purpose, e.g., coating, dipping, brushing, or by wet end addition, etc. The amount of polymer applied to the paper will generally vary within the range of about 1 to 8 percent (weight) pickup, depending upon the particular polymer and paper combination used and the degree of electroconductivity which is desired. ln some cases, still less might be used. There seems to be no operative upper limit to the amount of polymer applied, except to the extent this is determined by economics. It will therefore be appreciated and understood that the overall range of from about 1 percent to about 8 percent pickup (by weight) is simply a statement of the required amount of polymer to confer electroconductivity properties to the cellulosic web substrate which will adapt it to most commercial uses mentioned above.

The following examples are illustrative of the electroconductive papers of the present invention.

EXAMPLE 1 Separate sheets of a 40-pound bleached sulfite paper made from pulp beaten to a 450 ml. Canadian Standard Freeness is dipped into dilute solutions of the polymer of example A containing about 25 mole percent of dimethylaminoethyl methacrylate and about 75 mole percent of N-(B-hydroxyethyl)-N-(B-methacryloxyethyl)-N,N-dimethylammonium chloride units, and then passes through squeeze rolls to obtain conductive paper sheets with various amounts of this polymer to serve as a conductivity aid. After equilibration at appropriate relative humidities, the prepared papers are measured for surface resistivity. Results are shown in table l.

TABLE 1 Surface Resistivi-ty (ohms/square) Relative Humidity All these treated papers are suitable in conventional electrostatic photocopying equipment.

EXAMPLE 2 A solution of a homopolymer of N,N-dimethyl-N-(B- hydroxypropyl)-N-(fl-methacryloxyethyl)ammonium chloride having an estimated molecular weight of 50,000 viscosity average is applied to paper as in example 1 to provide 3 percent weight pickup. Surface resistivity is measured at 10 percent relative humidity and found to be 5X10 ohms/square. The resulting sheet is useful in xerographic reproduction machines.

EXAMPLE 3 Similar results are obtained by repeating example 2 using a homopolymer of N,N-diethyl-N-(l3-hydroxyethyl)-N-(B- acryloxyethyl)-ammonium chloride.

EXAMPLE 4 wherein R stands for hydrogen or methyl;

R represents a hydroxypropyl or hydroxyethyl group;

A represents a (C -C )-alkylene group;

R stands for a (C,-C )-alkyl group;

R stands for a (C -C )-alkyl group; and

X is a halogen anion.

2. The coated paper of claim 1, wherein the polymer contains units of the formula:

3. The coated paper of claim 1, wherein the polymer contains units of the formula:

4. The coated paper of claim 1, wherein said polymer contains units of the formula:

(HqCIl emu-mom l (Cmcm 2 wherein the symbols are as defined in claim 1.

6. A paper according to claim 2 wherein the polymer is a copolymer which also contains up to 25 mole percent of units, or salts thereof, of the formula:

(H11 7. A paper according to claim 3 wherein the polymer is a copolymer which also contains up to 25 mole percent of units. or salts thereof. of the formula:

8. A paper according to claim 4 wherein the polymer is a copolymer which also contains up to 25 mole percent of units, or salts thereof, of the formula:

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,617 ,372 Dated November 2, 1971 Inventor) Raymond W. McNamee, Jr. et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, at the end of line 30, insert or hydroxypropyl group,

Signed and sealed this 18th day of April 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents RM PO-105O 10-69 l USCOMM-DC eos7e-pe9 9 U 5 GOVERNMENT PRINTING OFFICE .969 DJBi-JJI 

2. The coated paper of claim 1, wherein the polymer contains units of the formula:
 3. The coated paper of claim 1, wherein the polymer contains units of the formula:
 4. The coated paper of claim 1, wherein said polymer contains units of the formula:
 5. A paper according to claim 1 in which the polymer is a copolymer of at least 75 mole percent of units of the formula of claim 1 and up to 25 mole percent of units, or salts thereof, of the formula: wherein the symbols are as defined in claim
 1. 6. A paper according to claim 2 wherein the polymer is a copolymer which also contains up to 25 mole percent of units, or salts thereof, of the formula:
 7. A paper according to claim 3 wherein the polymer is a copolymer which also contains up to 25 mole percent of units, or salts thereof, of the formula:
 8. A paper according to claim 4 wherein the polymer is a copolymer which also contains up to 25 mole percent of units, or salts thereof, of the formula: 